Over the past fifteen to twenty years, the potential dangers of hazardous waste, in general, and lead, in particular, have been the subject of community pressure, public awareness and ever stricter regulatory control in order to reduce or eliminate the dangers to people directly and to the surrounding environment and other media such as soil and air.
The leaching of lead into ground water is a grave concern because of the danger that the drinking water supplies and the environment will become contaminated. In addition, the danger of long term exposure to lead based paints in homes and buildings to the central nervous system of individuals and children, in particular, has now been well-documented.
40 C.F.R., Part 261.24(a), contains a list of contaminants and their associated maximum allowable concentrations. If a contaminant (such as lead) exceeds its maximum allowable concentration, then the material is classified as hazardous. In general, the toxicity characteristic leaching procedure ("TCLP") test determines whether a solid waste has unacceptable levels of certain hazardous substances such as lead which can be leached from the solid waste.
Waste containing leachable lead (Pb) is currently classified as hazardous waste due to the toxicity characteristic, if the level of lead extracted in a TCLP analysis is above 5.0 milligrams per liter (mg/L) or parts per millions (ppm).
Additionally, U.S. EPA land disposal restrictions prohibit the land disposal of solid wastes which leach in excess of these maximum allowable concentrations upon performance of the TCLP analysis. The land disposal regulations require that these wastes are treated until the heavy metals do not leach from the solid waste at levels above the maximum allowable concentrations prior to placement in a surface impoundment, waste pile, landfill or other land disposal unit as defined in 40 C.F.R. 260.10.
Furthermore, lead paint has been prohibited from residential and commercial buildings for a number of years. Rental apartments may not be rented to tenants without the elimination of lead paint from lower woodwork accessible to children. States have been unanimous across the country, in passing laws requiring the de-leading of rental property.
Property owners and banks which have taken over property under foreclosure are under a tremendous strain to clean up their properties.
Typically, only 25 micrograms of lead per deciliter of blood can affect the mental capacities of young children and can result in grave behavioral and physical problems. Incredibly, 52%, or about 42 million of the nations' households still have layers of lead based paint on their woodwork.
Lead is highly toxic, even in minute quantities. Once it is ingested, lead enters the bloodstream where it inhibits the production of hemoglobin which red blood cells need to carry oxygen. Lead also locks out essential enzymes in the brain and central nervous system to inactivate them. Symptoms of lead poisoning include abdominal pains, muscular weakness and fatigue, while severe exposure may cause nervous system disorders, high blood pressure and even death.
Young children are most vulnerable because their nervous systems and brains are still developing. Lead can be removed from humans by a process called chelation, using drugs that bind to the metal in the bloodstream and flush it out in the urine, if treatment is begun before too much damage is done.
However, medical treatment is no substitute for a safe environment. The Health and Human Services Agency plan calls for: (1) surveillance of children with elevated levels of lead in their blood; (2) elimination of leaded paint and contaminated dust in housing; (3) reduction of children's exposure to lead in food, air, soil and water; and (4) an increase in community programs for the prevention of childhood lead poisoning. Eliminating lead from all pre-1950 housing would save as much as $28 billion in medical expenses and other costs, but at an expense of about $10 billion to put this plan into effect over the next 10 years.
This combination of criteria for the removal and treatment of lead based paint and proper disposal of the resultant hazardous waste can pose a significant challenge for developing a specific treatment for a particular solid waste that will meet both the regulatory and disposal criteria. The present invention meets this dual role of treating a lead based paint waste so that it may be safely disposed of in a landfill.
For example, the traditional soil amendments which have been used for many physical requirements, i.e., lime or lime-based products such as Portland Cement, are high alkaline. While such solid waste may meet the TC criteria when measured using the buffered acidic TCLP leachate solution, amphoteric substances such as lead may leach significantly if disposed of under more neutral conditions.
Nor have prior art additives and mixtures been used to treat lead based paints. Unlike the present invention, prior art additives and mixtures for reducing the leachability of lead have been unable to obtain these results with either the use of one additive only or with its combination with Portland Cement.
U.S. Pat. No. 5,202,033 describes an insitu method of decreasing heavy metal leaching from solid waste using a combination of solid waste additives and additional pH controlling agents from the source of phosphate, carbonate, and sulfates.
U.S. Pat. No. 5,037,479 discloses a method for treating highly hazardous waste containing unacceptable levels of leachable metals such as lead by mixing the solid waste with a buffering agent selected from the group consisting of magnesium oxide, magnesium hydroxide, reactive calcium carbonates and reactive magnesium carbonates with an additional agent which is either an acid or salt containing an anion from the group consisting of Triple Superphosphate (TSP), ammonium phosphate, diammonium phosphate, phosphoric acid, boric acid and metallic iron.
U.S. Pat. No. 4,889,640 discloses a method and mixture for treating hazardous waste, including lead, by mixing the solid waste with an agent selected from the group consisting of reactive calcium carbonate, reactive magnesium carbonate and reactive calcium magnesium carbonate.
U.S. Pat. No. 4,652,381 discloses a process for treating industrial waste water contaminated with battery plant waste, such as sulfuric acid and heavy metals by treating the waste water with calcium carbonate, calcium sulfate, calcium hydroxide to complete a separation of the heavy metals. However, this is not for use in a landfill situation.
Various prior methods have also been used to detoxify, but not dispose of, lead based paint waste.
For example, U.S. Pat. No. 4,112,191 discloses metal salts of dithiocarbamates as effective precipitants for lead ions that can be included in a digestible coating which is applied over lead based paints to effectively detoxify the lead paint.
U.S. Pat. No. 4,305,853 discloses a process of chemically modifying metal oxides, such as lead oxide, by treating them under heat with a Lecithin material so that the metal oxides may obtain new and desirable properties.
U.S. Pat. No. 5,234,470 discloses a media for use in treating a surface to remove undesired contaminants, such as paint, that can be used to remove lead paint softened by conventional strippers.
U.S. Pat. No. 5,365,013 discloses a unit for the removal and disposal of lead painted woodwaste.
Unlike the present invention, however, none of the prior art solutions are able to utilize the lead based waste itself in combination with a single additive, either alone or with Portland Cement, to safely dispose of a lead based paint by producing a non-toxic landfill substance as defined by the TCLP.